Framing for drywall under Spiral staircase

Hi folks. As part of the never-ending basement renovation, I'm working on a framing plan for the basement staircase so I can get on with drywall. The main staircase (ground floor to upper level) is a curved, 90 degree turn construction, which from the underside presents a gentle S-shaped curve. The basement staircase, however, is a basic square, 90 degree consisting of two short flights and a landing which extends about 24" beyond the spiral stair stringer at the outside corner. Widest span I have to deal with is 68" from the inside curved wall to the outside farthest corner of the square landing.

I need to come up with a framing plan that will maximize headroom on the basement stairs and, of course, be strong enough to support the weight of drywall. My initial impression is that simply running 2x3s on edge across the bottom of the curved staircase stringers and extending to tie into the stud walls around the square basement stair landing would do the trick, paying close attention to framing everything level and no more than 24" on centre. (I'm envisioning some rather pie-shaped sections of framing around the bend, with straight sections (more or less) at either end). Scribed lines on both stud walls (inside curved and outside square) would act as guides to keep the smooth flow of framing.

My question here, in addition to whatever framing expertise is out there to help me plan this, is: Is it permissible to attach framing for drywall directly to the upper staircase to support the drywall in the middle of the span? I have had several drywall contractors in to quote the drywall job, and received conflicting answers to this. I am located in Ontario, btw.

I'm leaning on the 'permissible" side of this question myself as the original drywall framing had 2x3's nailed directly to the back of at least a few stair treads, but there's always the chance that the original builder "bent" the code on this one......

Can anyone offer their experience with curved staircases and/or their understanding of the Ontario Building Code?

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Framing for drywall under Spiral staircase

Thanks for the reply, thekctermite! . Below are some pics of the staircase - not good ones, but hopefully they'll give you a sense of what I'm dealing with.

For the most part, there is plenty of head room except for one spot. For most of the staircase the height measures 87" from top of basement stair tread to bottom of upper staircase tread, with the stringer on the outside edge sitting slightly lower at 84.5". The problem is the height at the top of the second flight of basement stairs - only 77" to the bottom of the stringer. Put a framing member below that and you're down to 73" with drywall......

Which is why I'm wondering if I can attach the drywall framing to the actual staircase instead of or in addition to the stud walls. A lot less headroom lost if I can......

Framing for drywall under Spiral staircase

Can't say as to code, but every one I've hung has had the framing members (generally 2"x4" laid flat, not on edge) fastened directly to the staircase however is was possible. The stairs are freestanding and need no structural support. The framing underneath is just to hold up the drywall. The drywall will have to be hung with 2 layers of 1/4" to allow it to bend and bow around the radius of the stairs. Having the widest part of the 2"x to fasten to makes it much easier to fasten as the pieces are difficult to get an exact measurement for. It's easiest to cut them on the large side and "whittle" them into place. The more "nailers" and the closer together, the better off you'll be. Be sure adhesive is used to minimize the amount of fasteners......

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Framing for drywall under Spiral staircase

Quote:

Originally Posted by bjbatlanta

Can't say as to code, but every one I've hung has had the framing members (generally 2"x4" laid flat, not on edge) fastened directly to the staircase however is was possible. The stairs are freestanding and need no structural support. The framing underneath is just to hold up the drywall. The drywall will have to be hung with 2 layers of 1/4" to allow it to bend and bow around the radius of the stairs. Having the widest part of the 2"x to fasten to makes it much easier to fasten as the pieces are difficult to get an exact measurement for. It's easiest to cut them on the large side and "whittle" them into place. The more "nailers" and the closer together, the better off you'll be. Be sure adhesive is used to minimize the amount of fasteners......

Good solid advice there! Code doesn't say you can't hang rock (or framing) directly to the stairs, I don't think it'll be a problem as long as the stairs are rock solid.

Framing for drywall under Spiral staircase

Thanks bjbatlanta. You've confirmed for me what I believe to be standard practice here in Ontario as well. I was second-guessing myself on this, as a contractor here to quote the drywall job said that tying the drywall directly to the stringers/staircase wouldn't meet code. I thought it was a bit odd, as almost every staircase I've ever seem opened up underneath has been done this way.... Maybe he wanted to amke a bit more work for himself?